WASHINGTON, Dec 1 (Reuters) - The U.S. government is raising its estimate of how many Americans are becoming infected with the AIDS virus every year by 50 percent, according to newspaper reports on Saturday.

The federal Centers for Disease Control and Prevention now believes the number of new HIV infections each year is between 55,000 and 60,000 -- up from the 40,000 figure used for the past decade, The Washington Post reported.

The Post cited two unidentified people in contact with the scientists preparing the new estimate.

It said the higher figures were based on data from 19 states and large cities that were extrapolated to the nation as a whole. The CDC has not made the new estimate public.

The Wall Street Journal also reported the CDC's expected upward revision, citing unidentified outside researchers and public health officials.

The Journal said Robert Janssen, director of the CDC's Division of HIV/AIDS Prevention, declined to comment on the new estimates, saying they could change.

The newspapers attributed the revision to new testing technology developed by the U.S. public health agency, which also revised its methodology to make estimates more precise.

"The higher estimate is the product of a new method of testing blood samples that can identify those who were infected within the previous five months. With a way to distinguish recent infections from long-standing ones, epidemiologists can then estimate how many new infections are appearing nationwide each month or year," the Post said. (Writing by Doina Chiacu; Editing by Richard Balmforth)

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